Automated optical inspection and sorting systems have been used to inspect and sort various target specimens including fruits and vegetables, processed meats, baked goods, and other foodstuffs, to separate different types of recyclable material, and to sort foreign or defective items from supplies of wood chips. These systems typically-employvideo cameras with charge-coupled device line scan cameras to acquire images of target specimens moved on a conveyor belt across an optical scanning area. Illumination of the specimens is generally provided by broad-spectrum tubular fluorescent lamps. Signal processing circuitry identifies variations in the shade of target specimen images and sorts target specimens accordingly.
Shipments of raisins from producers often include unwanted items such as raisin stems, leaves, and rocks. It is desirable to remove such contaminants before shipping raisins to consumers and as a check on the relative weight or volume of the unwanted items in shipments of raisins, which are usually purchased on the basis of weight and/or volume. When the raisins to be shipped to a consumer are to consist of dark raisins, it is also desirable to separate out golden raisins, which are grapes that were less mature before being picked and dried than the grapes that produce dark raisins and that are accordingly less sweet than dark raisins.
Conventional optical inspection and sorting systems using fluorescent lamps have not been used commercially to sort unwanted contaminants, e.g., grape stems and rocks, from a mixture including raisins and the contaminants because such systems cannot sort those contaminants from the mixture with sufficient accuracy to be commercially feasible.
One automated optical inspection system, the Elbiscan 5000 Laser system sold by Elbicon N. V., is effective for sorting rocks from a mixture including raisins and rocks. Its specifications indicate that it uses one or two lasers producing emissions in the red or in both the red and the green portions of the electromagnetic spectrum.